Neo4j Interview Questions And Answers

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Mindmajix as a team have got enough questions from the trainees who got their Neo4j Training and cracked interviews at various MNCs around the world and successfully placed. From the collection of Neo4j Interview questions, following are the most common questions we got are listed to make it easy for those who are willing to crack the interview with ease. All the answers to those were written by our professional experienced trainers and are tailored to meet the concepts expected by the interviewer.

Q. What is Neo4J?
It is an open source graph database used to connect rich data to get connected using graph powered systems in order to deliver accurate connectedness of available data. NOSQL is used to get data connected, with Java and scala implementation.

Q. Where do we use Neo4J?
While working with huge distributed databases.

Q. What is the IP we use to access Neo4J environment?
http://127.0.0.1:7474/

Q. Mention some important features of Neo4J.
Following are few important features:

• Data Representation using graph model
• Reliable ACID transactions.
• Quick and Durable.
• High Speed query execution for traversals.
• Easily accessible by REST or Java APIs.

Q. What does a Neo4J graph node stores?
Key-Value Pairs

Q. What is the Query Language used by Neo4J?
Cypher Query Language - CQL is used to execute queries for Neo4J.

Q. What kind of language is CQL.
There are two types of query languages - Procedural and declarative.
CQL is a Declarative Language.

Q. How do you  query language in Neo4J.
CQL is the language used in Neo4J and is inspired by SQL to explain graphs to understand easily. Commands like select, insert, update or delete helps one to mention graphs. We execute commands in “$” prompt environment.

Image source: https://neo4j.com/developer/cypher-query-language/

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Q. Explain structure of Neo4J query language with an example.
Matching patterns is easy while working with nodes using Neo4J.
Example: To get cast of actors starting with S

MATCH (actor:Person)-[:ACTED_IN]->(movie:Movie)
WHERE movie.title STARTS WITH "S"
RETURN movie.title AS title, collect(actor.name) AS cast
ORDER BY title ASC LIMIT 10;

Q. Mention few other famous graph database available?
Other available graph databases in the market are:

• Oracle NoSQL Database
• Sqrrl Enterprise
• Graph Story
• Titan
• Velocity Graph
• InfoGrid
• Bitsy
• Teradata Aster
• Oracle Spatial and Graph
• Info Grid and many more.

Q. List out some of Neo4J Commands you use.
There are many commands in Neo4J, of which following are few basic commands:

• CREATE - To create a node or relationship.
• MATCH - To read or retrieve all the nodes in the database.
• MERGE - Combination of CREATE and MATCH.
• SET - To add or update properties to new or existing node/relationships.
• CREATE UNIQUE - To mention unique constraints in order to avoid redundant values.

Q. What is REMOVE command used for?
To remove labels and properties of the nodes, we use REMOVE.

Q. What is the difference between REMOVE and DELETE commands?
Main difference is that REMOVE is for labels and properties of nodes, whereas DELETE is to remove nodes and relationships. 

Q. What is object Cache in Neo4J?
In order to improve the performance of the graph traversals, Object Cache is used to cache the nodes and their properties.

Q. What are the types of Object Cache in Neo4J?
There are two types of Object Cache which can also referred as High Level Cache:

• Reference Cache
• High Performance Cache(HPC)

Q. Command for updating properties or adding new properties to existing relationships?
SET is the command used to update or add properties to existing relationships.

Q. Neo4j Vs MongoDB?

Neo4j	MongoDB
Primary database model is Graph DBMS.	Primary database model is Document Store.
Implemented in Java and Scala.	Impleted in C++ Langauage.
Neo4j has optional schema.	MongoDB is schema-free.
It uses Cypher query language, Java API, Neo4j-OGM, Spring Data Neo4j, TinkerPop 3	Proprietary protocol using JSON
Uses triggers	No triggers are used

Q. Brief Neo4j CQL LIMIT clause?

For filtering or limiting the number of rows that return by a query, we use Neo4j CQL LIMIT clause.

Q. What  is the IN Operator syntax?

IN Operator Syntax: IN[ ]

Q. CREATE UNIQUE is used for?

CREATE UNIQUE used for fixing the graph structures.

Q. Which is fastest to handle graphs, MYSQL or Neo4j?

To handle graphs Neo4j is the fastest one compared to MYSQL.

Q. Which architecture allows for remote server?

REST architecture, that allows neo4j for remote servers.